Third Party shipping software linking?

[Mr. Escalade]

So here's something that I've been trying to figure out lately and wanted to know if anybody here might have an answer.

Let say I have several stealth and ghost accounts and I am using a third-party shipping software (such as Stamps.com or Endicia with Shipstation or Shipworks etc.) to both import my orders and to create shipping labels. The software will also be used to automatically upload the tracking info to the accounts.

Will my IP get linked to eBay and Amazon or will it go though the server of the software? Also, since the tracking numbers are very similar to each other, can they be linked?

I have also heard of Auctivia. Any reviews on their shipping capabilities? Can you for example print 1 oz letter rate labels with the Non-Machinable feature as you could with Endicia?

Thanks!